Due to the energy crisis and the increasing attention to environmental protection, a new energy automobile is the development direction of future automobiles. An electric automobile has been rapidly developed worldwide. Compared with a traditional internal combustion engine automobile, the electric automobile has better economy and environment friendliness, and has significant advantages in the environmental protection aspect due to the characteristic of almost zero emission. Meanwhile, due to the characteristics of a drive motor, such as rapid response, low speed, large torque and the like, the electric automobile has better acceleration performance; the rotation speed and the torque of the motor are easy to acquire; and the electric automobile may be controlled more accurately. Therefore, the electric automobile has great development potential.
The electric automobile is generally driven to run by adopting a power assembly composed of a motor and a drive axle or a power assembly composed of the motor, a transmission and the drive axle. Due to the defects of large unsprung mass, poor heat dissipation of a hub motor and the like, an electric automobile driven by the hub motor is not produced in large scale. Therefore, most of the power assemblies of existing electric automobiles include the drive axle.
A differential is an important component in the drive axle. Because of a “differential without differential torque” principle in the differential, a drive torque of the automobile may be only equally vectored to both sides of left and right wheels. In this way, ground adhesive force cannot be well utilized under the condition that ground adhesion is not uniform; and even slippage of the wheels and other unsteady running conditions may be easily caused on one side with low adhesion, so that the adhesive capability of drive wheels cannot be achieved. Meanwhile, when the automobile makes a turn at high speed, a load may be transferred from an inside wheel to an outside wheel. Even if the ground adhesion is good, the adhesive capability of the outside wheel may be higher than that of the inside wheel. At this moment, the torque is equally vectored to the inside and outside wheels by the traditional differential, which may cause that the inside wheel reaches an adhesion limit and slips, and the automobile is instable. If part of the torque of the inside wheel is transferred to the outside wheel, lateral force margin of the inside wheel may be increased to prevent the wheels from slipping, and an additional yawing moment may be generated for the complete vehicle. The yawing moment may help to promote and guide the vehicle to turn, thereby increasing turning maneuverability and ultimate turning capability of the vehicle. At present, the technology is applied to some high-end sports cars and high-grade SUVs in a form of a torque vectoring differential, such as a super handling all-wheel drive system (SH-AWD) developed by Honda Company, a super active yawing control (SAYC) system developed by Mitsubishi Corporation, and the like. However, the technology is not widely applied in the electric automobile.